Crescents and ripples

A piece of Mars: A lonely dune slowly makes its way (towards the upper right) across a plain. Well, look closer, it’s not all that lonely. Surrounding it on the plain are smaller streaks that are ripples, which also once worked their way across this plain. The smaller ripples are thought to be inactive, or at least far less active, than the larger dunes on Mars. (HiRISE ESP_029660_1350)